Development of processing diagrams for underfill resins

Underfill resins are used to reduce the solder fatigue in flip-chip assemblies. Both the underfilling and the curing process are crucial to the reliability of the finished products. A variety of techniques have been used to characterize the essential phenomena governing the processing of underfill resins. Such phenomena include wetting, flow behavior, cure kinetics, cure stresses, outgassing phenomena and void formation. We will show that processing diagrams for underfill resins can be developed based on these fundamentals and provide guidelines for the underfilling and curing steps. With such processing diagrams one should be able to design the underfilling and curing process using a scientific approach that allows one to save time and money from the usual trial and error method.